nervous tissue

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The brain and spinal cord make up which division of the nervous system?

Central Nervous System
The command and processing part of the NS, handles integration and motor output


This system includes all the neural tissue outside the CNS, afferent, efferent divisions, nerves and ganglia?

The Peripheral Nervous System


Definition of a nerve?

Bundle of nerve fibers(axons) wrapped in fibrous connect tissue.
Nerves carry signals to and from other organs of the body.


Definition of a ganglion?

A knotlike swelling of cell bodies of neurons contained in the PNS.
A group of cell bodies.


What is the difference between nuclei and ganglia?

In the CNS a collection of neuron cell bodies is called a NUCLEUS.
In the PNS a collection of neuron cell bodies is called a GANGLIA.


The functional unit of the nervous system is...?



The sensory(afferent) division of the PNS brings information TOWARDS the CNS?
True or false?

True, the sensory division brings sensory information towards the CNS from receptors in peripheral tissue and organs.


The motor(efferent) divison of the PNS carries brings information TOWARDS the CNS?
True or False?

False! the motor neurons carry motor commands(instructions) AWAY from the CNS to peripheral effectors, think: muscles and glands


True or false?
Neurons greatly outnumber neuroglia in neural tissue?

False!! Neuroglia-the "Glue" that holds the NS together OUTNUMBER neurons.
Neuroglia=supporting cells.


Definition of a TRACT?

White matter in the CNS that contains bundles of axons with common orgins, destinations and functions.
A Group of neurons traveling together in the CNS.


Name 4 physiological properties of neurons.

1. Excitability/Irritability-ability to respond to stimuli
2. Conductivity-Carry/transfer/conduct an electric impulse
3. Secretion-of a chemical neurotransmitter that simulates the next cell(Acetycholine ACh and norepinephrin)
4. Longevity-Extremely long lives, do not divide, will not make more. High metabolic rate-must receive constant nutrition(qlucose and oxygen) to stay energized


The Somatic Nervous system is considered to be voluntary?
True or False?

True- the Somatic Nervous System controls skeletal muscle, skin, and is "voluntary". Includes the motor system and actions like blinking.


The Autonomic Nervous system(ANS) contains which 2 additional systems?

The autonomic nervous system- regulates smooth and cardiac muscles and glands, "involuntary".


SYMPATHETIC NERVOUS SYSTEM, part of the ANS, function?

Conserves energy and maintains activity while the body is at rest,ex digestion. "Rest and digest"



Mobilizes the body under stress, "fight or flight"


Name 5 types of neuoglia cells in the CNS

1. Astrocytes-wrap around neurons, create and maintain a blood-brain barrier
2. Oligodendrocytes-responsible for forming the myelin sheath around several neural fibers
3. Nodes of Ranvier-small gaps between myelinated axons.
4. Microglia-responsible for cleaning waste and eliminate foreign matter (macrophages)
5. Ependymal cells-act as cushioning for the spinal cord and brain, produce and maintain cerebrospinal fluid


Name 4 types of neuroglia cells in the PNS

1. Satellite-Responsible for cleaning waste and regulating nutrion. Similar to astrocytes
2. Scwann-responsible for forming the myelin sheath around a single nerve fiber. Similar to Oligodendrocytes
3. Neurilemma-the outermost layer(basal lamina) of a Schwann cell, necessary for regeneration
4. Endoneurium- thin connective tissue sheath(alveolar tissuu) necessary for regeneration


What is a neuron made of?

1. Soma/cell body-contains the nucleus, cytoplasm, neurofilaments(neurofibrils-provide support) Nissl bodies-clusters of Rough Endoplasmic Reticulum and free ribosomes.
2. Dendrites-"tree like extensions" receive signals and conduct them to soma
3. Axon-an elongated fiber, carries signals away from the soma
4. Axon hillock-starts the transmission of a signal down the axon-controls the "firing" of the neuron. Also called an intial segement
5. Terminal knobs-responsible for sending a signal to other neurons


What is myelin?
Where is it found?

Myelin is an insulating sheath around nerve fibers(axons)
Found in Oligodendrocytes in the CNS
Found in Schwann cells in the PNS


Structural Classification of Neurons
Meaning of:

Anaxonic-axon and dendrites are indistinguishable. located in brain and special sense organs
Bipolar-single dendrite and axon with cell body between, located in special senses-smell, sight, hearing
Unipolar-dendrites and axon are continuous,located in pathways from the skins surface
Multipolar-multiple dendrites and a single axon, the MOST common in CNS. ALL skeletal muscle neurons are multipolar


True or false?
All skeletal muscle neurons are multipolar?

True! Multipolar neurons are the most common in the CNS and comprise all skeletal muscle


What are exteroceptors?

Exterocepters are sensory receptors that collect information about the outside world. Like touch, temperature, pressure, sight, smell and hearing.


What are proprioceptors?

Proprioceptors monitor the position and movement of skeletal muscles and joints, gives information by "experience"(angle of a joint, stretch of muscle), used to detect "where you are in space"


What are ineroceptors?

Interoceptors are sensory receptors that collect information about internal systems like digestive, respiratory, cardiovascular, urinary and reproductive systems. Sensation of taste, deep pressure and pain.


The Autonomic Nervous System(ANS) contains visceral motor neurons?
True or false?

True! The autonomic nervous system controls cardiac and smooth muscle and glands.
Controls at a subconscious level "involuntary"
Contains 2 neurons:
1. preganglionic neurons-originates in the CNS, sends fibers to glangionic neurons in autonomic ganglia
2. ganglionic neurons-sends postganglionic fibers to effector


True or false?
Interneurons are found only in the Central Nervous System?

True! Interneurons are found between sensory and motor neurons, ONLY in the CNS.
Interneurons are responsible for distribution of sensory information and coordination of motor activity.
Involved in functions like memory, planning and learning.


The Central Nervous System and Peripheral Nervous System neurons are each capable of REGENERATING?

False!! The CNS is NOT capable of any type of regeneration.
Schwann Cells found only in the PNS can stimulate axon regrowth,


Conduction velocity, how fast a nerve impulse travels, depends on the length of the axon and macrophages?

FALSE! The conduction velocity is affected by:
1. the presence or lack of a myelin sheath
2. diameter of the axon
If there is no myelin sheath the nerve impulse will move MUCH slower!


What is a synapse and what kinds are there?

A synapse is a site of communication between a neuron and another cell, muscle or gland.
1. Electric
2. Chemical


Describe an electrical synapse

Electrical synapses are gap junctions that link cells. Found in CARDIAC and some smooth muscle.
Very rapid cell transmission and no decision making is necessary, involuntary
ex- Intercalated discs in cardiac muscle, reacts like "the wave" in a stadium,
Electrical impulses are faster than chemical impulses


Describe a chemical synapse

Chemical synapses require a neurotransmitter.
1. An arriving electrical impulse stimulates the release of a neurotransmitter by the presynaptic neuron.
2. The neurotransmitter crosses the synaptic cleft(a space)
3. Receptors on post synaptic membrane bind with neurotransmitter. Must have CALCIUM for this to occur
4. Effect-muscle cells contract, glands secrete, action potential is reached.
5. Chemical synapses are much more common than electrical synapses, there can be thousands of chemical synapses on the surface of a single neuron


Axoaxonic synapses

Synapse that is formed between the axon of a presynaptic neuron and the axon of a postsynaptic neuron


Axodendritic synapses

Presynaptic neurons form on the dendrites of postsynaptic neurons
Most common synapse, the CNS typically has thousands of axodendritic synapses


Axosomatic synapses

Presynaptic neurons terminate on the soma of the postsynaptic neuron


Name 2 common neurotransmitters

are the most common neurotransmitters


Neurons function in groups called "neuronal pools?"

True-Collections of neurons for a certain purpose. Ex-breathing, sensory perception.
Within a pool neurons are connected by pathways called NEURONAL CIRCUITS


Types of neural organization

1. Divergence-spread of information from one neuron to many.
ex-visual information arrives from the eyes and is spread to many areas such as posture control and balance
2. Parallel-occurs after divergence, allows many responses to occur at the same time.
ex-step on a sharp rock- you may
withdraw your foot
shift your weight
move your arms
feel pain
ALL at the same TIME


Types of neural processing

1. Serial processing- several neurons synapse on the SAME postsynaptic neuron
ex. your breathing is subconscious, BUT you can also control when you hold your breath or breath more deeply
2. Reverberating-use of positve feedback, gives continual output


True or false?
The Central Nervous System is the control center for ALL human activities?

False! The CNS is an excellent control center but it does not control EVERYTHING, (certain things are processed by the endocrine system and at the cellular level)


True or false?
Over 20% of the Central Nervous system is extracellular space?

False! Nervous tissue is VERY cellular and less than 20% is extracellular space.